Audio connectors, such as a stereo plug-in Tip Ring Sleeve (TRS), are widely used in electronic terminal devices, for example, as the output interfaces for audio source player devices, such as CD, VCD, DVD, and MP3. Audio connectors have become the most widely used audio interfaces. There are three common audio interfaces: 2.5 mm, 3.5 mm, and 6.3 mm audio interfaces. On an audio device, the TIP is used to connect the left audio channel, the RING is used to connect the right audio channel, and the SLEEVE is used to connect the ground. The profile of a TRS audio connector interface is small, and thus the interface occupies a small area on the external interface of the device.
The serial port enjoys the advantages of simple transmission protocols and easy-to-implement physical electric features, and plays a key role in development, commissioning, repair, and maintenance of electronic terminal devices. For example, the RS232-based serial ports are widely used in PCs to transmit serial signals. The outgoing serial ports of electronic terminal devices, such as PC and set top box (STB), are DB-9 or DE-9 connectors. The port profile of the DB-9 connector is about 30×15 mm, which occupies a large space.
Certain electronic terminal devices can transmit data through infrared, and need to receive and send infrared signals that carry data. Certain electronic terminal devices are equipped with remote controls, and can receive and send infrared signals through the remote controls. Therefore, electronic terminal devices need to receive or send infrared signals.
Customers have high requirements for shape and dimensions of electronic terminal devices now. According to the traditional method, to implement commissioning through serial ports, the DB-9 interface must be reserved on the terminal. But this leads to constraints on the shape and dimensions of the terminal, and unpleasant appearance of the terminal. If no interfaces are reserved at the external surface of the device, the connection socket for serial ports must be reserved on the internal circuit board, or a multi-pin connector must be adopted. If the socket is reserved on the circuit board, however, the device shell must be opened every time during commissioning, board development test, and repair and maintenance so that the serial port can be used, thus reducing the work efficiency.
In existing technologies, interfaces can be shared by using a multi-pin connector. Specifically, a non-standard multi-pin connector is adopted. For example, a 6-pin connector is used. Among which, 3 pins are allocated for serial port connection and the other 3 pins are allocated for infrared connection. These pins are not multiplexed between each other. This method implements sharing of multiple functional interfaces, and avoids large-dimension DB-9. However, the pins are defined by the vendor, and need to be customized, thus increasing the cost. In addition, this method does not apply to a device with strict ID control, for example, when no non-standard self-defined pins are allowed.
For certain electronic terminal devices with standard interfaces such as USB interfaces, the USB interfaces can be converted into serial ports through a USB cable.
The price for implementing such conversion through this method is high. For compatibility implementation based on electric features, the standard interfaces such as USB interfaces must be reconstructed; or protocol conversion is required, thus implementing virtual serial communication. However, this makes the software complicated and increases the difficulty in maintenance. In addition, the serial port function depends on the normal running of the USB interfaces, thus limiting the scenarios of the serial ports and reducing maintainability.